Providing additional cage space to monkeys housed in research settings may positively affect their behavior, but there are few, relevant empirical studies. Here, we made two comparisons using archival data. The first assessed the effect that a second cage had on abnormal behavior of 72 single-housed rhesus macaques (Macaca mulatta), 3-22 years old. We collected data thrice weekly using one-zero scan sampling (mean duration 10-min) and compared the first 12 weeks with additional cage access to the 12-weeks prior. Additional space did not change the occurrence of abnormal behavior (Wilcoxon Z = -0.60, p = 0.55). There was also no change when we examined just stereotypic behaviors (Z = -1.04, p = 0.30). The second assessment was on a subset of five subjects with additional behavioral monitoring due to histories of self-injurious behavior (5-min focal observations, twice monthly; total 300 minutes). When given additional cage access, all five showed a decrease in time devoted to abnormal behavior (10.06% to 3.98%) (Wilcoxon Z = -2.02, p = 0.04). While not statistically significant, four of the five decreased stereotypic behavior (Z = -1.83, p = 0.07) and three of the five decreased self-biting (Z = -1.83, p = 0.07). Our findings do not show an improvement in abnormal behavior in general, but individuals with more severe abnormal behavior may benefit from additional space.